Rubber compositions comprising benzoquinones and the use thereof in golf balls

ABSTRACT

The present invention is directed to a golf ball having at least one layer formed from a rubber composition comprising a base rubber, at least 0.05 parts by weight of a free radical initiator, per 100 parts of the base rubber, and at least 0.1 parts by weight of a benzoquinone, per 100 parts of the base rubber. The rubber composition may be present in any one or more of a core layer, a cover layer, or an intermediate layer.

FIELD OF THE INVENTION

The present invention is directed to rubber compositions comprising abase rubber, at least 0.05 parts by weight of a free radical initiator,per 100 parts of the base rubber, and at least 0.10 parts by weight of abenzoquinone, per 100 parts of the base rubber. The present invention isalso directed to the use of such compositions in golf equipment.

BACKGROUND OF THE INVENTION

Benzoquinones

The use of benzoquinones in rubber-based golf ball compositions isknown. For example, U.S. Pat. No. 6,339,119 to Ladd et al. discloses agolf ball containing a cover layer and a core layer, where the corelayer is molded from a scorch retarding composition comprising a scorchretarding peroxide, an elastomeric polymer, and a crosslinking agent.The scorch retarding peroxide typically contains a free radicalscavenger selected from the group consisting of benzoquinones,hydroquinones, phenols, benzaldehydes, cyclohexadiene-1-ones, andmixtures thereof. The amount of the free radical scavenger in the scorchretarding peroxide is preferably from about 0.01 parts to about 2 partsper 100 parts of the peroxide by weight.

U.S. Pat. No. 6,767,940 to Voorheis et al. is directed to a golf ballhaving a core and cover, particularly to a golf ball core formed from acomposition including an elastomeric polymer, a free radical initiator,and at least one stable free radical. The composition can furtherinclude one or more free radical scavengers and scorch retarders toincrease the scorch time of the elastomeric polymer. Suitable freeradical scavengers include benzoquinones; hydroquinones; phenols;benzaldehydes; cyclohexadiene-1-ones; and mixtures thereof.

Additional background references include U.S. Pat. No. 6,919,393 to Manoet al., U.S. Pat. No. 6,956,128 to Higuchi et al., U.S. PatentApplication Publication No. 2002/0052253 to Fushihara et al., and U.S.Pat. No. 6,488,597 to Iwami et al.

Resilient Cores

The primary source of resilience, as measured by coefficient ofrestitution (“COR”), in commercially available golf balls ispolybutadiene rubber, which is generally used to form all or part of thecore. It is known that the resilience of a golf ball core, at a givencompression, may be increased by forming a core layer from a rubbercomposition comprising an organosulfur compound. However, organosulfurcompounds can be expensive and can cause processing difficulties.

Thus, a desire remains in the golf ball industry for novel rubbercompositions having high resilience at a given compression. The presentinvention provides such compositions and their use in a variety of golfball core, cover, and intermediate layers.

SUMMARY OF THE INVENTION

In one embodiment, the present invention is directed to a golf ballcomprising a core and a cover, the core having at least one layer formedfrom a rubber composition comprising a base rubber, a free radicalinitiator, and a benzoquinone. The free radical initiator is present inthe rubber composition in an amount of at least 0.05 parts by weight per100 parts of the base rubber, and the benzoquinone is present in therubber composition in an amount of at least 0.15 parts by weight per 100parts of the base rubber.

In another embodiment, the present invention is directed to a golf ballcomprising a core and a cover, the core having at least one layer formedfrom a rubber composition comprising a baser rubber, a free radicalinitiator, and a benzoquinone. The free radical initiator is present inthe rubber composition in an amount of at least 0.05 parts by weight per100 parts of the base rubber and the benzoquinone is present in therubber composition in an amount of at least 0.1 parts by weight per 100parts of the base rubber. The benzoquinone is selected from compoundsrepresented by the following formula, and hydrates thereof:

wherein each R₁, R₂, R₃, and R₄ is independently selected from the groupconsisting of: a metal salt of a carboxyl group (e.g., —COO⁻M⁺), anacetate group (—CH₂COOH) and esters thereof (—CH₂COOR), a hydroxy group(—OH), a metal salt of a hydroxy group (e.g., —O⁻M⁺), an amino group(—NH₂), a nitro group (—NO₂), an aryl group (e.g., phenyl, tolyl, etc.),an aryloxy group (e.g., phenoxy, etc.), an arylalkyl group [e.g., cumyl(—C(CH₃)₂phenyl); benzyl (—CH₂ phenyl)], a nitroso group (—NO), anacetamido group (—NHCOCH₃), and a vinyl group (—CH═CH₂).

In another embodiment, the present invention is directed to a golf ballcomprising a core and a cover, the core having at least one layer formedfrom a rubber composition comprising a base rubber, a free radicalinitiator, a benzoquinone, and substantially free of organosulfurcompounds. The free radical initiator is present in the rubbercomposition in an amount of at least 0.05 parts by weight per 100 partsof the base rubber, the benzoquinone is present in the rubbercomposition in an amount of at least 0.15 parts by weight per 100 partsof the base rubber, and a ratio of the amount of the benzoquinonepresent in the rubber composition to the amount of free radicalinitiator present in the rubber composition is from 0.25 to 2. Thebenzoquinone is selected from compounds represented by the followingformula, and hydrates thereof:

wherein each R₁, R₂, R₃, and R₄ is independently selected from the groupconsisting of hydrogen, a halogen group (F, Cl, Br, I), an alkyl group,a carboxyl group (—COOH) and metal salts thereof (e.g., —COO⁻M⁺) andesters thereof (—COOR), an acetate group (—CH₂COOH) and esters thereof(—CH₂COOR), a formyl group (—CHO), an acyl group (—COR), an acetyl group(—COCH₃), a halogenated carbonyl group (—COX), a sulfo group (—SO₃H) andesters thereof (—SO₃R), a halogenated sulfonyl group (—SO₂X), a sulfinogroup (—SO₂H), an alkylsulfinyl group (—SOR), a carbamoyl group(—CONH₂), a halogenated alkyl group, a cyano group (—CN), an alkoxygroup (—OR), a hydroxy group (—OH) and metal salts thereof (e.g.,—O⁻M⁺), an amino group (—NH₂), a nitro group (—NO₂), an aryl group(e.g., phenyl, tolyl, etc.), an aryloxy group (e.g., phenoxy, etc.), anarylalkyl group [e.g., cumyl (—C(CH₃)₂phenyl); benzyl (—CH₂ phenyl)], anitroso group (—NO), an acetamido group (—NHCOCH₃), and a vinyl group(—CH═CH₂).

DETAILED DESCRIPTION OF THE INVENTION

Golf balls of the present invention include one-piece, two-piece (i.e.,solid core and a cover), multi-layer (i.e., solid core of one or morelayers and/or a cover of one or more layers), and wound golf ballshaving a variety of core structures, intermediate layers, covers, andcoatings. Golf ball cores may consist of a single, unitary layer,comprising the entire core from the center of the core to its outerperiphery, or they may consist of a center surrounded by at least oneouter core layer. The center, innermost portion of the core ispreferably solid, but may be hollow or liquid-, gel-, or gas-filled. Theouter core layer may be solid, or it may be a wound layer formed of atensioned elastomeric material. Golf ball covers may also contain one ormore layers, such as a double cover having an inner and outer coverlayer. Optionally, additional layers may be disposed between the coreand cover.

Golf balls of the present invention have at least one layer which isformed from a rubber composition of the present invention. In aparticular embodiment, the rubber composition of the present inventionis present in at least one core layer of a two-piece or multi-layer golfball.

Rubber Composition

Rubber compositions of the present invention comprise a base rubber, atleast one free radical initiator, and at least one free radicalscavenger.

The base rubber is selected from natural and synthetic rubbers andmixtures thereof, including, but not limited to, polybutadiene; mixturesof two or more polybutadienes; styrene-butadiene; mixtures of two ormore polybutadienes and styrene-butadiene; and mixtures ofpolybutadiene(s) with one or more additional rubbers selected fromnatural rubber, polyisoprene rubber, ethylene propylene rubber, ethylenepropylene diene rubber, styrene-butadiene rubber, styrenic blockcopolymer rubbers (such as SI, SIS, SB, SBS, SIBS, and the like, where“S” is styrene, “I” is isobutylene, and “B” is butadiene), butyl rubber,halobutyl rubber, polystyrene elastomers, polyethylene elastomers,polyurethane elastomers, polyurea elastomers, metallocene-catalyzedelastomers, and plastomers. When the base rubber is a mixture ofpolybutadiene and at least one additional rubber, the amount ofpolybutadiene in the mixture is preferably at least 40 wt %, based onthe total weight of the mixture. In a particular embodiment, the baserubber is polybutadiene. Suitable examples of commercially availablepolybutadienes include, but are not limited to, Buna CB 23, commerciallyavailable from LANXESS Corporation; SE BR-1220, commercially availablefrom The Dow Chemical Company; Europrenes NEOCIS® BR 40 and BR 60,commercially available from Polimeri Europa; UBEPOL-BR® rubbers,commercially available from UBE Industries, Ltd.; and BR 01 commerciallyavailable from Japan Synthetic Rubber Co., Ltd.

The free radical initiator is selected from organic peroxides, highenergy radiation sources capable of generating free radicals, andcombinations thereof. Suitable organic peroxides include, but are notlimited to, dicumyl peroxide; n-butyl-4,4-di(t-butylperoxy) valerate;1,1-di(t-butylperoxy)3,3,5-trimethylcyclohexane;2,5-dimethyl-2,5-di(t-butylperoxy) hexane; di-t-butyl peroxide;di-t-amyl peroxide; t-butyl peroxide; t-butyl cumyl peroxide;2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3;di(2-t-butyl-peroxyisopropyl)benzene; dilauroyl peroxide; dibenzoylperoxide; t-butyl hydroperoxide; and combinations thereof. In aparticular embodiment, the free radical initiator is dicumyl peroxide,including, but not limited to Perkadox® BC, commercially available fromAkzo Nobel. Peroxide free radical initiators are generally present inthe rubber composition in an amount of at least 0.05 parts by weight per100 parts of the base rubber, or an amount within the range having alower limit of 0.05 parts or 0.1 parts or 1 part or 1.25 parts or 1.5parts by weight per 100 parts of the base rubber, and an upper limit of2.5 parts or 3 parts or 5 parts or 6 parts or 10 parts or 15 parts byweight per 100 parts of the base rubber.

Coagents are commonly used with peroxides to increase the state of cure.Suitable coagents include, but are not limited to, metal salts ofunsaturated carboxylic acids having from 3 to 8 carbon atoms;unsaturated vinyl compounds and polyfunctional monomers (e.g.,trimethylolpropane trimethacrylate); phenylene bismaleimide; andcombinations thereof. Particular examples of suitable metal saltsinclude, but are not limited to, one or more metal salts of acrylates,diacrylates, methacrylates, and dimethacrylates, wherein the metal isselected from magnesium, calcium, zinc, aluminum, lithium, and nickel.In a particular embodiment, the coagent is selected from zinc salts ofacrylates, diacrylates, methacrylates, and dimethacrylates. In anotherparticular embodiment, the coagent is zinc diacrylate. When the coagentis zinc diacrylate and/or zinc dimethacrylate, the coagent is typicallyincluded in the rubber composition in an amount within the range havinga lower limit of 1 part or 5 parts or 10 parts by weight per 100 partsof the base rubber, and an upper limit of 19 parts or 20 parts or 25parts or 30 parts or 35 parts or 40 parts or 45 parts or 50 parts or 60parts by weight per 100 parts of the base rubber. When one or more lessactive coagents are used, such as zinc monomethacrylate and variousliquid acrylates and methacrylates, the amount of less active coagentused may be the same as or higher than for zinc diacrylate and zincdimethacrylate coagents.

Curing agents may also be used in compositions of the present invention.Curing agents include, but are not limited to, sulfur; N-oxydiethylene2-benzothiazole sulfenamide; N,N-di-ortho-tolylguanidine; bismuthdimethyldithiocarbamate; N-cyclohexyl 2-benzothiazole sulfenamide;N,N-diphenylguanidine; 4-morpholinyl-2-benzothiazole disulfide;dipentamethylenethiuram hexasulfide; thiuram disulfides;mercaptobenzothiazoles; sulfenamides; dithiocarbamates; thiuramsulfides; guanidines; thioureas; xanthates; dithiophosphates;aldehyde-amines; dibenzothiazyl disulfide; tetraethylthiuram disulfide;tetrabutylthiuram disulfide; and combinations thereof.

High energy radiation sources capable of generating free radicalsinclude, but are not limited to, electron beams, ultra-violet radiation,gamma radiation, X-ray radiation, infrared radiation, heat, andcombinations thereof.

Further examples of suitable free radical initiators, coagents, andcuring agents are disclosed in U.S. Patent Application Publication Nos.2004/0214661 and 2003/0144087 and U.S. Pat. Nos. 6,566,483, 6,695,718,and 6,939,907, the entire disclosures of which are hereby incorporatedherein by reference.

Rubber compositions of the present invention comprise at least one freeradical scavenger. In a preferred embodiment, the free radical scavengeris a benzoquinone compound. In a particularly preferred embodiment, thefree radical scavenger is a benzoquinone compound selected from one ormore compounds represented by the following formula, and hydratesthereof:

wherein each R₁, R₂, R₃, and R₄ is independently selected from the groupconsisting of hydrogen, a halogen group (F, Cl, Br, I), an alkyl group,a carboxyl group (—COOH) and metal salts thereof (e.g., —COO⁻M⁺) andesters thereof (—COOR), an acetate group (—CH₂COOH) and esters thereof(—CH₂COOR), a formyl group (—CHO), an acyl group (—COR), an acetyl group(—COCH₃), a halogenated carbonyl group (—COX), a sulfo group (—SO₃H) andesters thereof (—SO₃R), a halogenated sulfonyl group (—SO₂X), a sulfinogroup (—SO₂H), an alkylsulfinyl group (—SOR), a carbamoyl group(—CONH₂), a halogenated alkyl group, a cyano group (—CN), an alkoxygroup (—OR), a hydroxy group (—OH) and metal salts thereof (e.g.,—O⁻M⁺), an amino group (—NH₂), a nitro group (—NO₂), an aryl group(e.g., phenyl, tolyl, etc.), an aryloxy group (e.g., phenoxy, etc.), anarylalkyl group [e.g., cumyl (—C(CH₃)₂phenyl); benzyl (—CH₂ phenyl)], anitroso group (—NO), an acetamido group (—NHCOCH₃), and a vinyl group(—CH═CH₂).

In another particularly preferred embodiment, the free radical scavengeris a benzoquinone compound selected from one or more compoundsrepresented by the following formula, and hydrates thereof:

wherein each R₁, R₂, R₃, and R₄ is independently selected from the groupconsisting of: a metal salt of a carboxyl group (e.g., —COO⁻M⁺), anacetate group (—CH₂COOH) and esters thereof (—CH₂COOR), a hydroxy group(—OH), a metal salt of a hydroxy group (e.g., —O⁻M⁺), an amino group(—NH₂), a nitro group (—NO₂), an aryl group (e.g., phenyl, tolyl, etc.),an aryloxy group (e.g., phenoxy, etc.), an arylalkyl group [e.g., cumyl(—C(CH₃)₂phenyl); benzyl (—CH₂ phenyl)], a nitroso group (—NO), anacetamido group (—NHCOCH₃), and a vinyl group (—CH═CH₂).

In another particularly preferred embodiment, the free radical scavengeris a benzoquinone selected from methyl p-benzoquinone and tetrachlorop-benzoquinone.

The free radical scavenger may be a combination of two or morebenzoquinones, each of which is independently selected from compoundsrepresented by one of the above formulas. The free radical scavenger mayalso be a combination of one or more benzoquinones and one or morenon-benzoquinone free radical scavengers, including, but not limited to,hydroquinones, quinhydrones, catechols, and resorcinols.

The free radical scavenger is typically used in the form of a liquid orsolid. In a particular embodiment, the free radical scavenger is used ina solid form and may be synthesized or processed so as to have aparticle size of 0.25 mm or less, or 0.125 mm or less, or 0.09 mm orless. In another particular embodiment, the free radical scavenger isused in a solid form and melts at 150° F. or less, or 120° F. or less,or at a temperature that is the same as or less than the mixingtemperature of the base rubber.

The free radical scavenger is present in the rubber composition in anamount of at least 0.1 parts by weight or at least 0.15 parts by weightor at least 0.2 parts by weight per 100 parts of the base rubber, or anamount within the range having a lower limit of 0.1 parts or 0.15 partsor 0.25 parts or 0.3 parts or 0.375 parts by weight per 100 parts of thebase rubber, and an upper limit of 0.5 parts or 1 part or 1.5 parts or 2parts or 3 parts by weight per 100 parts of the base rubber.

In a particular embodiment, a ratio (P_(BQ)/P_(FRI)) of the amount(P_(BQ)) of the benzoquinone present in the rubber composition, measuredin parts by weight per 100 parts of the base rubber, to the amount(P_(FRI)) of free radical initiator present in the rubber composition,measured in parts by weight per 100 parts of the base rubber, is from0.05 to 2. In another embodiment, P_(BQ)/P_(FRI) is at least 0.05 andless than 0.5. In another embodiment, P_(BQ)/P_(FRI) is at least 0.2 andless than 0.5. In another embodiment, P_(BQ)/P_(FRI) is at least 0.25and less than 0.5. In yet another embodiment, P_(BQ)/P_(FRI) is withinthe range having a lower limit of 0.05 or 0.2 or 0.25 and an upper limitof 0.4 or 0.45 or 0.5 or 2.

Rubber compositions of the present invention optionally contain one ormore antioxidants. Some antioxidants also act as free radicalscavengers. Thus, when antioxidants are included in the rubbercomposition, the amount of free radical initiator used may be as high orhigher than the amounts disclosed herein.

Rubber compositions of the present invention optionally contain one ormore particulate fillers selected from inorganic fillers, such as zincoxide, titanium dioxide, tin oxide, calcium oxide, magnesium oxide,barium sulfate, zinc sulfate, calcium carbonate, zinc carbonate, bariumcarbonate, mica, talc, clay, silica, lead silicate, and the like; highspecific gravity metal powder fillers, such as tungsten powder,molybdenum powder, and the like; regrind, i.e., core material that isground and recycled; and nano-fillers. The amount of particulatematerial(s) present in rubber compositions of the present invention istypically within the range having a lower limit of 5 parts or 10 partsby weight per 100 parts of the base rubber, and an upper limit of 30parts or 50 parts or 100 parts by weight per 100 parts of the baserubber.

Rubber compositions of the present invention optionally contain one ormore additives selected from processing aids, processing oils,plasticizers, coloring agents, fluorescent agents, chemical blowing andfoaming agents, defoaming agents, stabilizers, softening agents, impactmodifiers, and the like. The amount of additive(s) typically present inrubber compositions of the present invention is typically within therange having a lower limit of 0 parts by weight per 100 parts of thebase rubber and an upper limit of 20 parts or 50 parts or 100 parts or150 parts by weight per 100 parts of the base rubber.

Filler materials may be dual-functional fillers, for example, zinc oxide(which may be used as a filler/acid scavenger) and titanium dioxide(which may be used as a filler/brightener material). Further examples ofsuitable fillers and additives include, but are not limited to, thosedisclosed in U.S. Patent Application Publication No. 2003/0225197, theentire disclosure of which is hereby incorporated herein by reference.

Rubber compositions of the present invention may have one or more of thefollowing properties relative to previously known golf ballcompositions: higher resilience, lower compression, increased resilienceat equal compression, decreased compression at equal resilience, reducedcrystallinity, increase in glass transition temperature, and an“S-shaped” shift in the rheometer curve.

In some embodiments, rubber compositions of the present invention have acombination of compression and COR values, as measured on golf ballcores formed from the rubber composition, previously achieved by addingorganosulfur compounds to rubber compositions. In some embodiments,rubber compositions of the present invention have a combination ofcompression and COR values, as measured on golf ball cores formed fromthe rubber composition, superior to previously known compositions. Thus,rubber compositions of the present invention may contain one or moreorganosulfur compounds, but can have desirable compression and CORproperties without them. Suitable organosulfur compounds are more fullydisclosed, for example, in U.S. Pat. Nos. 6,635,716 and 6,919,393, theentire disclosures of which are hereby incorporated herein by reference.In a particular embodiment, the rubber composition is substantially freeof organosulfur compounds. “Substantially free,” as used herein, meansthat the rubber composition does not contain an organosulfur compound,or includes one or more organosulfur compounds in an amount of less than0.01 parts by weight per 100 parts of the base rubber.

The present invention is not limited by any particular method for makingthe rubber composition.

Rubber compositions of the present invention can be used in a variety ofapplications. For example, rubber compositions of the present inventionare suitable for use in golf equipment, including, but not limited to,golf balls, golf shoes, and golf clubs.

Golf Ball Applications

Golf balls of the present invention include one-piece, two-piece,multi-layer, and wound golf balls, having at least one layer which isformed from a rubber composition of the present invention. In golf ballshaving two or more layers which comprise a rubber composition of thepresent invention, the rubber composition of one layer may be the sameor a different rubber composition as another layer. The layer(s) formedfrom the rubber composition of the present invention can be any one ormore of a core layer, a cover layer, or an intermediate layer disposedbetween a core and a cover.

Golf ball cores of the present invention include single, dual, andmultilayer cores, and preferably have an overall diameter within therange having a lower limit of 0.75 inches or 1 inch or 1.25 inches or1.4 inches and an upper limit of 1.55 inches or 1.6 inches or 1.62inches or 1.63 inches. Dual and multilayer cores have an inner corelayer and an outer core layer, and multilayer cores additionally have atleast one intermediate core layer disposed between the inner core layerand the outer core layer. Inner core layers of the present inventionpreferably have a diameter within the range having a lower limit of 0.5inches or 0.75 inches or 1 inch and an upper limit of 1.25 inches or 1.4inches or 1.55 inches or 1.57 inches or 1.58 inches. Outer core layersof the present invention preferably have a thickness within the rangehaving a lower limit of 0.02 inches or 0.025 inches or 0.032 inches andan upper limit of 0.31 inches or 0.44 inches or 0.56 inches. The totalthickness of intermediate core layer(s) of the present invention ispreferably within the range having a lower limit of 0.02 inches or 0.025inches or 0.032 inches and an upper limit of 0.15 inches or 0.22 inchesor 0.28 inches.

Golf ball cores of the present invention preferably have an Atticompression of 110 or less, or 90 or less, or 80 or less, or 75 or less,or 70 or less, or 65 or less, or 60 or less, or 50 or less. Compressionis measured according to the procedure set forth below. Golf ball coresof the present invention preferably have a COR at 125 ft/s of at least0.775, or at least 0.780, or at least 0.782, or at least 0.785, or atleast 0.787, or at least 0.790, or at least 0.795, or at least 0.800.COR is determined according to the procedure set forth below. In aparticular embodiment, the present invention provides a golf ball corehaving an Atti compression of 75 or less and a COR at 125 ft/s of atleast 0.8. In another particular embodiment, the present inventionprovides a golf ball core having an Atti compression of 75 or less and aCOR at 125 ft/s of at least 0.798. In another particular embodiment, thepresent invention provides a golf ball core having an Atti compressionof 60 or less and a COR at 125 ft/s of at least 0.785. In anotherparticular embodiment, the present invention provides a golf ball corehaving an Atti compression of 50 or less and a COR at 125 ft/s of atleast 0.781, or at least 0.783, or at least 0.790.

Golf balls of the present invention preferably have at least one corelayer formed from a rubber composition of the present invention. In aparticular embodiment, the present invention provides a golf ball havinga single layer core formed from a rubber composition of the presentinvention. In another particular embodiment, the present inventionprovides a golf ball comprising a dual core having an inner core layerand an outer core layer, wherein the inner core layer is formed from arubber composition of the present invention. In another particularembodiment, the present invention provides a golf ball comprising a dualcore having an inner core layer and an outer core layer, wherein theouter core layer is formed from a rubber composition of the presentinvention. In another particular embodiment, the present inventionprovides a golf ball comprising a multilayer core having an inner corelayer, an outer core layer, and at least one intermediate core layer,wherein the inner core layer is formed from a rubber composition of thepresent invention. In another particular embodiment, the presentinvention provides a golf ball comprising a multilayer core having aninner core layer, an outer core layer, and at least one intermediatecore layer, wherein the outer core layer is formed from a rubbercomposition of the present invention. In another particular embodiment,the present invention provides a golf ball comprising a multilayer corehaving an inner core layer, an outer core layer, and at least oneintermediate core layer, wherein an intermediate core layer is formedfrom a rubber composition of the present invention.

In yet another particular embodiment, the present invention provides awound golf ball comprising one or more core layers, an elastomericwinding around the core, and a cover, wherein a rubber composition ofthe present invention is present in at least one of the core layer(s)and/or the elastomeric winding around the core. Wound golf balls,including methods of their manufacture, are further disclosed, forexample, in U.S. Pat. No. 4,846,910, the entire disclosure of which ishereby incorporated herein by reference.

Golf ball cores of the present invention may include one or more layersformed from a suitable material other than a rubber composition of thepresent invention. Suitable core materials for the golf balls disclosedherein include, but are not limited to, natural and synthetic rubbers,such as polybutadiene, polyisoprene, ethylene propylene rubber, ethylenepropylene diene rubber, styrene-butadiene rubber, styrenic blockcopolymer rubbers (such as SI, SIS, SB, SBS, SIBS, and the like, where“S” is styrene, “I” is isobutylene, and “B” is butadiene), butyl rubber,halobutyl rubber, copolymers of isobutylene and para-alkylstyrene,halogenated copolymers of isobutylene and para-alkylstyrene, copolymersof butadiene with acrylonitrile, polychloroprene, alkyl acrylate rubber,chlorinated isoprene rubber, and acrylonitrile chlorinated isoprenerubber; metallocene polymers; acid copolymers and ionomers; andcombinations thereof.

Golf ball covers of the present invention include single, dual, andmultilayer covers, and preferably have an overall thickness within therange having a lower limit of 0.01 inches or 0.02 inches or 0.025 inchesor 0.03 inches or 0.04 inches or 0.045 inches or 0.05 inches or 0.06inches and an upper limit of 0.07 inches or 0.075 inches or 0.08 inchesor 0.09 inches or 0.1 inches or 0.15 inches or 0.2 inches or 0.3 inchesor 0.5 inches. Dual and multilayer covers have an inner cover layer andan outer cover layer, and multilayer covers additionally have at leastone intermediate cover layer disposed between the inner cover layer andthe outer cover layer. Inner cover layers of the present inventionpreferably have a thickness within the range having a lower limit of0.01 inches or 0.02 inches or 0.025 inches and an upper limit of 0.05inches or 0.15 inches or 0.2 inches. Outer cover layers of the presentinvention preferably have a thickness of 0.01 inches or 0.02 inches or0.025 inches and an upper limit of 0.05 inches or 0.15 inches or 0.2inches. Intermediate cover layer(s) of the present invention preferablyhave a thickness of 0.01 inches or 0.02 inches or 0.025 inches and anupper limit of 0.05 inches or 0.15 inches or 0.2 inches.

Golf ball covers of the present invention may include one or more layersformed from a suitable material other than a rubber composition of thepresent invention. The cover material is preferably a tough,cut-resistant material, selected based on the desired performancecharacteristics. Suitable cover materials for the golf balls disclosedherein include, but are not limited to, polyethylene, including, forexample, low density polyethylene, linear low density polyethylene, andhigh density polyethylene; polypropylene; rubber-toughened olefinpolymers; acid copolymers which do not become part of an ionomericcopolymer; plastomers; flexomers; styrene/butadiene/styrene blockcopolymers; styrene/ethylene-butylene/styrene block copolymers;dynamically vulcanized elastomers; ethylene vinyl acetates; ethylenemethyl acrylates; polyvinyl chloride resins; polyamides, amide-esterelastomers, and graft copolymers of ionomer and polyamide, including,for example, Pebax® thermoplastic polyether block amides, commerciallyavailable from Arkema Inc; crosslinked transpolyisoprene blends;polyurethanes; polyureas; polyester-based thermoplastic elastomers, suchas Hytrel®, commercially available from E. I. du Pont de Nemours andCompany; polyurethane-based thermoplastic elastomers, such asElastollan®, commercially available from BASF; synthetic or naturalvulcanized rubber; ionomeric resins; and combinations thereof. Suitablecover materials and constructions also include, but are not limited to,those disclosed in U.S. Pat. Nos. 6,117,025, 6,767,940, and 6,960,630,the entire disclosures of which are hereby incorporated herein byreference.

Commercially available ionomeric cover materials include, but are notlimited to, Surlyn® ionomer resins and DuPont® HPF 1000 and HPF 2000,commercially available from E. I. du Pont de Nemours and Company; andIotek® ionomers, commercially available from ExxonMobil ChemicalCompany. Also suitable are blends of ionomers with thermoplasticelastomers. Suitable ionomeric cover materials are further disclosed,for example, in U.S. Pat. Nos. 6,653,382, 6,756,436, 6,894,098,6,919,393, and 6,953,820, the entire disclosures of which are herebyincorporated by reference.

Suitable polyurethane cover materials are further disclosed, forexample, in U.S. Pat. No. 6,756,436, the entire disclosure of which ishereby incorporated herein by reference. When used as cover materials,polyurethane and polyurea can be thermoset or thermoplastic. Thermosetmaterials can be formed into golf ball layers by conventional casting orreaction injection molding techniques. Thermoplastic materials can beformed into golf ball layers by conventional compression or injectionmolding techniques. Light stable polyurethanes and polyureas are apreferred material for single layer covers and the outer cover layer ofdual and multilayer covers. High modulus thermoplastics are a preferredmaterial for the inner cover layer of dual and multilayer covers.

Golf ball cover materials optionally contain one or more filler(s), suchas the fillers given above for rubber compositions of the presentinvention (e.g., titanium dioxide, barium sulfate, etc.), and/oradditive(s), such as coloring agents, fluorescent agents, whiteningagents, antioxidants, dispersants, UV absorbers, light stabilizers,plasticizers, surfactants, viscosity modifiers, compatibility agents,foaming agents, reinforcing agents, release agents, and the like.

Golf balls of the present invention optionally include one or moreintermediate layer(s) disposed between the core and the cover. Whenpresent, the overall thickness of the intermediate layer(s) is generallywithin the range having a lower limit of 0.01 inches or 0.05 inches or0.1 inches and an upper limit of 0.3 inches or 0.35 inches or 0.4inches. Suitable intermediate layer materials include, but are notlimited to, natural rubbers, balata, gutta-percha, cis-polybutadienes,trans-polybutadienes, synthetic polyisoprenes, polyoctenamers,styrene-propylene-diene rubbers, metallocene rubbers, styrene-butadienerubbers, ethylene-propylenes, chloroprene rubbers, acrylonitrilerubbers, acrylonitrile-butadiene rubbers, styrene-ethylene blockcopolymers, maleic anhydride or succinate modified metallocene catalyzedethylene copolymers, polypropylene resins, ionomer resins, polyamides,polyesters, polyurethanes, polyureas, chlorinated polyethylenes,polysulfide rubbers, fluorocarbons, and combinations thereof.

Suitable golf ball constructions and materials are further disclosed,for example, in U.S. Patent Application Publication Nos. 2003/0144087and 2005/0164810, U.S. Pat. Nos. 5,688,119 and 5,919,100, and PCTPublications WO00/23519 and WO00/29129. The entire disclosure of each ofthese references is hereby incorporated herein by reference.

Golf balls of the present invention preferably have an overall diameterwithin the range having a lower limit of 1.6 or 1.62 or 1.66 inches andan upper limit of 1.69 or 1.74 or 1.800 inches. More preferably, golfballs of the present invention have an overall diameter of 1.68 inches.Golf balls of the present invention preferably have an Atti compressionof 120 or less, or 110 or less, or 105 or less. Golf balls of thepresent invention preferably have a COR at 125 ft/s of at least 0.75, orat least 0.78, or at least 0.79.

The present invention is not limited by any particular process forforming the golf ball layer(s). It should be understood that thelayer(s) can be formed by any suitable technique, including injectionmolding, compression molding, casting, and reaction injection molding.

EXAMPLES

It should be understood that the examples below are for illustrativepurposes only. In no manner is the present invention limited to thespecific disclosures therein.

Golf ball cores of the present invention were prepared by mixingmaterials according to the formulations given in the Tables below, andthen molding and grinding the resulting compositions to obtain 1.55 inchdiameter spheres. The compression and COR of each sphere was measuredand compared to the compression and COR of comparative spheres todetermine SFI. The results are given in the Tables below.

Compression, also referred to herein as “Atti compression,” is measuredaccording to a known procedure, using an Atti compression test device,wherein a piston is used to compress a ball against a spring. The travelof the piston is fixed and the deflection of the spring is measured. Themeasurement of the deflection of the spring does not begin with itscontact with the ball; rather, there is an offset of approximately thefirst 1.25 mm (0.05 inches) of the spring's deflection. Very lowstiffness cores will not cause the spring to deflect by more than 1.25mm and therefore have a zero Atti compression measurement. The Atticompression tester is designed to measure objects having a diameter of42.7 mm (1.68 inches); thus, smaller objects, such as golf ball cores,must be shimmed to a total height of 42.7 mm to obtain an accuratereading.

COR is determined according to a known procedure wherein a golf ball orgolf ball subassembly (e.g., a golf ball core) is fired from an aircannon at a given velocity (125 ft/s for purposes of the presentinvention). Ballistic light screens are located between the air cannonand the steel plate to measure ball velocity. As the ball travels towardthe steel plate, it activates each light screen, and the time at eachlight screen is measured. This provides an incoming transit time periodproportional to the ball's incoming velocity. The ball impacts the steelplate and rebounds though the light screens, which again measure thetime period required to transit between the light screens. This providesan outgoing transit time period proportional to the ball's outgoingvelocity. COR is then calculated as the ratio of the outgoing transittime period to the incoming transit time period, COR=T_(out)/T_(in).

SFI is determined by the following procedure. A control line is definedby the linear regression equation of COR vs. compression for two or morecontrol formulations. The regression equation is used to calculate theCOR of a theoretical control formulation at the same compression as anexample formulation. SFI is then calculated as the COR of the exampleformulation minus the COR of the theoretical control formulation at thesame compression as the example formulation. Thus, SFI is a positivenumber when the example formulation is more resilient than the controlline at the same compression, and a negative number when the exampleformulation is less resilient than the control line at the samecompression.

Examples 1-5 methyl p-benzoguinone as a Free Radical Scavenger

In Examples 1-5, rubber compositions of the present invention wereprepared by mixing SE BR-1220, methyl p-benzoquinone, Perkadox® BC,SR526, zinc oxide, and barium sulfate, in a Brabender mixer for 5-10minutes. Comparative compositions C1-C3 were similarly prepared, exceptthat no benzoquinone was added. The relative amount of each componentused is indicated in Table 1.

The rubber compositions of Examples 1-5 and C1-C3 were then cured in acompression molding press at 335° C. for 11 minutes to obtain spheres,which were subsequently ground to a diameter of 1.55 inches.

Each of the resulting spheres was evaluated for Atti compression and CORat 125 ft/sec. The SFI of each of Examples 1-5 was then determined bycomparing the compression and COR of each Example with the compressionand COR of C1-C3, according to the SFI procedure described above. Theresults for compression, COR, and SFI are reported in Table 1. TABLE 1Example No. 1 2 3 4 5 C1 C2 C3 Composition SE BR-1220* 100 100 100 100100 100 100 100 (parts by weight) methyl p-benzoquinone 0.75 0.5 0.5 1 10 0 0 (parts by weight) Perkadox ® BC** 3 2 3 4 3 0.5 0.5 0.5 (parts byweight) SR526*** 25 25 25 25 25 20 25 30 (parts by weight) zinc oxide 55 5 5 5 5 5 5 (parts by weight) barium sulfate 17.5 17.3 17.4 17.7 17.519 17.4 15.7 (parts by weight) P_(BQ)/P_(FRI) 0.25 0.25 0.17 0.25 0.33P_(BQ) = 0 P_(BQ) = 0 P_(BQ) = 0 Core Properties Compression 39 40 48 3626 34 61 81 COR 0.783 0.780 0.785 0.784 0.776 0.773 0.791 0.801 SFI0.006 0.003 0.003 0.009 0.007 — — —*SE BR-1220 is a high cis-1,4 polybutadiene commercially available fromThe Dow Chemical Company.**Perkadox ® BC is a dicumyl peroxide free radical initiatorcommercially available from Akzo Nobel.***SR526 is a zinc diacrylate-based coagent commercially available fromSartomer Company, Inc.

Example 6 tetrachloro p-benzoguinone as a Free Radical Scavenger

In Example 6, a rubber composition of the present invention was preparedby mixing SE BR-1220, tetrachloro p-benzoquinone, Perkadox® BC, SR526,zinc oxide, and barium sulfate, in a Brabender mixer for 5-10 minutes.Comparative compositions C4-C6 were similarly prepared, except that nobenzoquinone was added. The relative amount of each component used isindicated in Table 2.

The rubber compositions of Examples 6 and C4-C6 were then cured in acompression molding press at 335° C. for 11 minutes to obtain spheres,which were subsequently ground to a diameter of 1.55 inches.

Each of the resulting spheres was evaluated for Atti compression and CORat 125 ft/sec. The SFI of Example 6 was then determined by comparing thecompression and COR of Example 6 with the compression and COR of C4-C6,according to the SFI procedure described above. The results forcompression, COR, and SFI are reported in Table 2. TABLE 2 Example No. 6C4 C5 C6 Composition SE BR-1220* 100 100 100 100 (parts by weight)tetrachloro p-benzoquinone 0.5 0 0 0 (parts by weight) Perkadox ® BC** 20.5 0.5 0.5 (parts by weight) SR526*** 25 20 25 30 (parts by weight)zinc oxide 5 5 5 5 (parts by weight) barium sulfate 17.3 19.0 17.3 15.7(parts by weight) P_(BQ)/P_(FRI) 0.25 P_(BQ) = 0 P_(BQ) = 0 P_(BQ) = 0Core Properties Compression 53 31 58 80 COR 0.790 0.770 0.786 0.797 SFI0.008 — — —*SE BR-1220 is a high cis-1,4 polybutadiene commercially available fromThe Dow Chemical Company.**Perkadox ® BC is a dicumyl peroxide free radical initiatorcommercially available from Akzo Nobel.***SR526 is a zinc diacrylate-based coagent commercially available fromSartomer Company, Inc.

All patents, publications, test procedures, and other references citedherein, including priority documents, are fully incorporated byreference to the extent such disclosure is not inconsistent with thisinvention.

While the illustrative embodiments of the invention have been describedwith particularity, it will be understood that various othermodifications will be apparent to and can be readily made by those ofordinary skill in the art without departing from the spirit and scope ofthe invention. Accordingly, it is not intended that the scope of theclaims appended hereto be limited to the examples and descriptions setforth herein, but rather that the claims be construed as encompassingall of the features of patentable novelty which reside in the presentinvention, including all features which would be treated as equivalentsthereof by those of ordinary skill in the art to which the inventionpertains.

1. A golf ball comprising a core and a cover, wherein the core has atleast one layer formed from a rubber composition comprising: (a) a baserubber; (b) at least 0.05 parts by weight of a free radical initiatorper 100 parts of the base rubber; and (c) at least 0.15 parts by weightof a benzoquinone per 100 parts of the base rubber.
 2. The golf ball ofclaim 1, wherein a ratio (P_(BQ)/P_(FRI)) of the amount of thebenzoquinone present in the rubber composition (P_(BQ)), measured inparts by weight per 100 parts of the base rubber, to the amount of freeradical initiator present in the rubber composition (P_(FRI)), measuredin parts by weight per 100 parts of the base rubber, is from 0.05 to 2.3. The golf ball of claim 2, wherein P_(BQ)/P_(FRI) is from 0.25 to 2.4. The golf ball of claim 2, wherein P_(BQ)/P_(FRI) is at least 0.05 andless than 0.5.
 5. The golf ball of claim 2, wherein P_(BQ)/P_(FRI) is atleast 0.25 and less than 0.5.
 6. The golf ball of claim 2, whereinP_(BQ)/P_(FRI) is from 0.25 to 0.45.
 7. The golf ball of claim 1,wherein the benzoquinone is selected from compounds represented by thefollowing formula, and hydrates thereof:

wherein each R₁, R₂, R₃, and R₄ is independently selected from the groupconsisting of hydrogen, a halogen group (F, Cl, Br, I), an alkyl group,a carboxyl group (—COOH) and metal salts thereof (e.g., —COO⁻M⁺) andesters thereof (—COOR), an acetate group (—CH₂COOH) and esters thereof(—CH₂COOR), a formyl group (—CHO), an acyl group (—COR), an acetyl group(—COCH₃), a halogenated carbonyl group (—COX), a sulfo group (—SO₃H) andesters thereof (—SO₃R), a halogenated sulfonyl group (—SO₂X), a sulfinogroup (—SO₂H), an alkylsulfinyl group (—SOR), a carbamoyl group(—CONH₂), a halogenated alkyl group, a cyano group (—CN), an alkoxygroup (—OR), a hydroxy group (—OH) and metal salts thereof (e.g.,—O⁻M⁺), an amino group (—NH₂), a nitro group (—NO₂), an aryl group(e.g., phenyl, tolyl, etc.), an aryloxy group (e.g., phenoxy, etc.), anarylalkyl group [e.g., cumyl (—C(CH₃)₂phenyl); benzyl (—CH₂ phenyl)], anitroso group (—NO), an acetamido group (—NHCOCH₃), and a vinyl group(—CH═CH₂).
 8. The golf ball of claim 1, wherein the benzoquinone isselected from methyl p-benzoquinone and tetrachloro p-benzoquinone. 9.The golf ball of claim 1, wherein the rubber composition comprises oneor more coagents selected from metal salts of acrylates, diacrylates,methacrylates, and dimethacrylates, wherein the metal is selected frommagnesium, calcium, zinc, aluminum, lithium, and nickel; and wherein thetotal amount of metal salts of acrylates, diacrylates, methacrylates,and dimethacrylates present in the rubber composition is less than 20parts per 100 parts of the base rubber.
 10. The golf ball of claim 1,wherein the rubber composition is substantially free of organosulfurcompounds.
 11. The golf ball of claim 1, wherein the amount of thebenzoquinone present in the rubber composition is at least 0.2 parts byweight per 100 parts of the base rubber.
 12. The golf ball of claim 1,wherein the core is a single layer.
 13. The golf ball of claim 1,wherein the core comprises an inner core layer and an outer core layer,and wherein the inner core layer is formed from the rubber composition.14. The golf ball of claim 1, wherein the core comprises an inner corelayer and an outer core layer, and wherein the outer core layer isformed from the rubber composition
 15. A golf ball comprising a core anda cover, wherein the core has at least one layer formed from a rubbercomposition comprising: (a) a base rubber; (b) at least 0.05 parts byweight of a free radical initiator per 100 parts of the base rubber; and(c) at least 0.1 parts by weight of a benzoquinone per 100 parts of thebase rubber, wherein the benzoquinone is selected from compoundsrepresented by the following formula, and hydrates thereof:

wherein each R₁, R₂, R₃, and R₄ is independently selected from the groupconsisting of: a metal salt of a carboxyl group (e.g., —COO⁻M⁺), anacetate group (—CH₂COOH) and esters thereof (—CH₂COOR), a hydroxy group(—OH), a metal salt of a hydroxy group (e.g., —O⁻M⁺), an amino group(—NH₂), a nitro group (—NO₂), an aryl group (e.g., phenyl, tolyl, etc.),an aryloxy group (e.g., phenoxy, etc.), an arylalkyl group [e.g., cumyl(—C(CH₃)₂phenyl); benzyl (—CH₂ phenyl)], a nitroso group (—NO), anacetamido group (—NHCOCH₃), and a vinyl group (—CH═CH₂).
 16. The golfball of claim 15, wherein the rubber composition comprises at least 0.2parts by weight of the benzoquinone per 100 parts of the base rubber.17. The golf ball of claim 15, wherein a ratio (P_(BQ)/P_(FRI)) of theamount of the benzoquinone present in the rubber composition (P_(BQ)),measured in parts by weight per 100 parts of the base rubber, to theamount of free radical initiator present in the rubber composition(P_(FRI)), measured in parts by weight per 100 parts of the base rubber,is at least 0.05.
 18. The golf ball of claim 15, wherein the rubbercomposition is substantially free of organosulfur compounds.
 19. A golfball comprising a core and a cover, wherein the core has at least onelayer formed from a rubber composition comprising: (a) a base rubber;(b) at least 0.05 parts by weight of a free radical initiator, per 100parts of the base rubber; and (c) at least 0.15 parts by weight of abenzoquinone, per 100 parts of the base rubber; wherein the benzoquinoneis selected from compounds represented by the following formula, andhydrates thereof:

wherein each R₁, R₂, R₃, and R₄ is independently selected from the groupconsisting of hydrogen, a halogen group (F, Cl, Br, I), an alkyl group,a carboxyl group (—COOH) and metal salts thereof (e.g., —COO⁻M⁺) andesters thereof (—COOR), an acetate group (—CH₂COOH) and esters thereof(—CH₂COOR), a formyl group (—CHO), an acyl group (—COR), an acetyl group(—COCH₃), a halogenated carbonyl group (—COX), a sulfo group (—SO₃H) andesters thereof (—SO₃R), a halogenated sulfonyl group (—SO₂X), a sulfinogroup (—SO₂H), an alkylsulfinyl group (—SOR), a carbamoyl group(—CONH₂), a halogenated alkyl group, a cyano group (—CN), an alkoxygroup (—OR), a hydroxy group (—OH) and metal salts thereof (e.g.,—O⁻M⁺), an amino group (—NH₂), a nitro group (—NO₂), an aryl group(e.g., phenyl, tolyl, etc.), an aryloxy group (e.g., phenoxy, etc.), anarylalkyl group [e.g., cumyl (—C(CH₃)₂phenyl); benzyl (—CH₂ phenyl)], anitroso group (—NO), an acetamido group (—NHCOCH₃), and a vinyl group(—CH═CH₂); wherein a ratio (P_(BQ)/P_(FRI)) of the amount of thebenzoquinone present in the rubber composition (P_(BQ)), measured inparts by weight per 100 parts of the base rubber, to the amount of freeradical initiator present in the rubber composition (P_(FRI)), measuredin parts by weight per 100 parts of the base rubber, is from 0.25 to 2;and wherein the rubber composition is substantially free of organosulfurcompounds.
 20. The golf ball of claim 19, wherein P_(BQ)/P_(FRI) is atleast 0.25 and less than 0.5.